The permeation of oxygen ions through ceramic ion transport membranes is the basis for a variety of gas separation devices and oxidation reactor systems operating at high temperatures in which permeated oxygen is recovered on the permeate side as a high purity oxygen product or is reacted on the permeate side with oxidizable compounds to form oxidized or partially oxidized products. The practical application of these gas separation devices and oxidation reactor systems requires membrane assemblies having large surface areas, means to contact feed gas with the feed sides of the membranes, and means to withdraw product gas from the permeate sides of the membranes. These membrane assemblies may comprise a large number of individual membranes arranged and assembled into modules having appropriate gas flow piping to introduce feed gas into the modules and withdraw product gas from the modules.
Ion transport membranes may be fabricated in either planar or tubular configurations. In the planar configuration, multiple flat ceramic plates are fabricated and assembled into stacks or modules having piping means to pass feed gas over the planar membranes and to withdraw product gas from the permeate side of the planar membranes. In tubular configurations, multiple ceramic tubes may be arranged in bayonet or shell-and-tube configurations with appropriate tube sheet assemblies to isolate the feed and permeate sides of the multiple tubes.
The individual membranes used in planar or tubular module configurations typically comprise very thin layers of active membrane material supported on material having large pores or channels that allow gas flow to and from the surfaces of the active membrane layers. The ceramic membrane material and the components of the membrane modules can be subjected to significant mechanical stresses during normal steady-state operation and especially during unsteady-state startup, shutdown, and upset conditions. These stresses may be caused by thermal expansion and contraction of the ceramic material and by dimensional variance caused by chemical composition or crystal structure changes due to changes in the oxygen stoichiometry of the membrane material. These modules may operate with significant pressure differentials across the membrane and membrane seals, and stresses caused by these pressure differentials must be taken into account in membrane module design. In addition, the relative importance of these phenomena may differ depending on whether the modules are operated in gas separation or oxidation service. The potential operating problems caused by these phenomena may have a significant negative impact on the purity of recovered products and on membrane operating life.
There is a need in the field of high temperature ceramic membrane reactor systems for new membrane module and vessel designs that address and overcome these potential operating problems. Such designs should include features to allow efficient operation, long membrane life, minimum capital cost, and the ability to specify membrane systems over a wide range of production rates. Embodiments of the invention disclosed herein address these design problems and include improved module and vessel designs for both oxygen production and oxidation systems.